A Level Maths Mechanics Help pls
Last Question of my HW and im stuck pls help asap its due tomorrow 
In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:
a) the acceleration of the competitor
b) her speed at the instant she passes P
In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:
a) the acceleration of the competitor
b) her speed at the instant she passes P
(edited 3 years ago)
Original post by MikeOxlong69
Last Question of my HW and im stuck pls help asap its due tomorrow
In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:
a) the acceleration of the competitor
b) her speed at the instant she passes
In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:
a) the acceleration of the competitor
b) her speed at the instant she passes
Which suvat equation(s) might be useful? What do you know/don't know?
(edited 3 years ago)
i know 5 suvat equation which are as follows:
u = v - at
2s/(u+v) = t
v^2 = U^2 + 2as
s = Vt - (1/2)at^2
S = ut + (1/2)at^2
i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.
u = v - at
2s/(u+v) = t
v^2 = U^2 + 2as
s = Vt - (1/2)at^2
S = ut + (1/2)at^2
i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.
Original post by MikeOxlong69
i know 5 suvat equation which are as follows:
u = v - at
2s/(u+v) = t
v^2 = U^2 + 2as
s = Vt - (1/2)at^2
S = ut + (1/2)at^2
i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.
u = v - at
2s/(u+v) = t
v^2 = U^2 + 2as
s = Vt - (1/2)at^2
S = ut + (1/2)at^2
i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.
Agreed you have two bits of information, s and t and you want to solve for a.
However, you have two sets of such information. Can you think how you can use two (possible the same equation with different s and t) to eliminate the need for the third bit of information.
Id concentrate on the last equation and think about P->Q and P->R.
Original post by MikeOxlong69
Last Question of my HW and im stuck pls help asap its due tomorrow
In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:
a) the acceleration of the competitor
b) her speed at the instant she passes B
In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:
a) the acceleration of the competitor
b) her speed at the instant she passes B
Looks pretty simple.
S = 2.4+11.5
T=2.5hrs
A=?
U=0
What eqtn can you use?
Original post by boulderingislife
Looks pretty simple.
S = 2.4+11.5
T=2.5hrs
A=?
U=0
What eqtn can you use?
S = 2.4+11.5
T=2.5hrs
A=?
U=0
What eqtn can you use?
It doesn't say u=0 anywhere?
Original post by mqb2766
It doesn't say u=0 anywhere?
You’re right. I just (probably falsely) assumed the runner started from rest.
oh i see now - its simultaneous equations
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
(edited 3 years ago)
Original post by MikeOxlong69
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
We don't know what point is actually meant for (b): you wrote B but that point is never mentioned or defined in the rest of the question.
Original post by MikeOxlong69
oh i see now - its simultaneous equations
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
Units need converting.
Original post by DFranklin
We don't know what point is actually meant fthor (b): you wrote B but that point is never mentioned or defined in the rest of the question.
thanks for spotting that, i'll change the original post now
its meant to say P
Original post by MikeOxlong69
oh i see now - its simultaneous equations
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
Not checked the vslues , but right approach. Sub back in if you want to check.
In a) you could just eliminate u and solve for a.
Then in b), you could find u, assuming that's the question asked - passing through P?
Original post by MikeOxlong69
thanks for spotting that, i'll change the original post now
its meant to say P
its meant to say P
You are right with the simultaneous eqtns but use km/hr or m/s, not both. Your answer looks like it should be in kh/h?
Original post by boulderingislife
Units need converting.
omg im so dumb lol
when u solve the equations u get the following:
u = 0.293 kmh^-1
a = 4.2 kmh^-2
which when converted to SI units gives:
u = 0.293*1000*(3600)^-1 = 0.0814 ms^-1
a = 4.2*1000*(3600)^-2 = 3.24*10^-4 ms^-2
Original post by MikeOxlong69
omg im so dumb lol
when u solve the equations u get the following:
u = 0.293 kmh^-1
a = 4.2 kmh^-2
which when converted to SI units gives:
u = 0.293*1000*(3600)^-1 = 0.0814 ms^-1
a = 4.2*1000*(3600)^-2 = 3.24*10^-4 ms^-2
when u solve the equations u get the following:
u = 0.293 kmh^-1
a = 4.2 kmh^-2
which when converted to SI units gives:
u = 0.293*1000*(3600)^-1 = 0.0814 ms^-1
a = 4.2*1000*(3600)^-2 = 3.24*10^-4 ms^-2
and then i guess for part b the answer is 0.0814 ms^-1
right????
@boulderingislife
@mqb2766
(edited 3 years ago)
Original post by MikeOxlong69
oh i see now - its simultaneous equations
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
i got these equations:
2.4 = u+ (1/2)a
13.9 = 2.5u + 3.125a
solved this for:
u = 0.293 ms^-1
a = 4.2 ms^-2
and then for b:
isnt it just 0.293 ms^-1??
because we worked that out in part a no??
let me know if this is right
Above is m/s. Km/hr is fine as long as you use the correct units 😜
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